In general, a wireless communication system can increase performance using channel information about a transmitter. For example, a wireless communication system operating in Frequency Division Duplexing (FDD) (hereinafter, referred to as an FDD system) uses different frequencies on uplink and downlink. Since an uplink channel and a downlink channel are independent of each other in the FDD system, a receiver should transmit channel information to a transmitter.
In the FDD system, for example, the receiver quantizes the channel information, taking into account a limited feedback capacity and transmits the quantized channel information to the transmitter. In this case, the transmitter may receive incorrect channel information having a quantization error. This incorrect channel information may degrade system performance.
Such performance degradation may occur significantly from an interference channel. Accordingly, the FDD system needs a technique for efficiently using a limited feedback capacity for an interference channel between transmitters.
In general, a feedback scheme for an interference channel is based on the premise that a transmitter and a receiver are predetermined.
For example, in a cellular system, User Equipments (UEs) to receive a service are predetermined on a Base Station (BS) basis. Therefore, various feedback schemes may be available for a BS to provide a service to predetermined UEs.
For example, in a situation where a transmitter and a receiver are preset, every UE quantizes channel information and provides a predetermined amount of feedback information to a BS. The BS selects at least one UE based on the feedback information received from all UEs. The BS may select the at least one UE in such a manner that the sum of total data rates may be maximized.
However, the foregoing UE selection scheme is not suitable for a specific VCN system. The specific VCN system may be a system in which a plurality of distributed small BSs share a plurality of UEs in one physical space. The physical space may be a macro cell serviced by a macro BS.
What channel information each UE should feed back to which distributed small BS in the VCN system has not been specified yet. Because each UE may receive a service from one of a plurality of distributed small BSs, it is difficult to determine what channel information to be quantized and fed back.
Conventionally, the amount of feedback information is equal for each UE, with no regard to the characteristics of UEs and data. As a result, resources are unnecessarily consumed for feedback.
In this context, there is a pressing need for developing a feedback scheme that can be efficiently combined with a virtual cell formation scheme in a VCN system. That is, there is a need for a method for forming a virtual cell and allocating feedback bits such that performance degradation caused by incorrect channel information may be minimized.
Considering that various types of content and various services are provided in wireless communication systems, it is necessary to design a feedback scheme in consideration of the characteristics of UEs and data.
The above information is presented as background information only to assist with an understanding of the present disclosure. No determination has been made, and no assertion is made, as to whether any of the above might be applicable as prior art with regard to the present disclosure.